Dairy Wastewater Treatment Using Membrane Bioreactor

Abstract

Abstract The paper presents the results of scientific researches in the field of biomembrane treatment of dairy products industry enterprises wastewater. Practical experiments confirmed the possibility of reducing the inhibition degree of the process of biological treatment of dairy products industry wastewater, which has been physically and chemically purified, by increasing the concentration of active sludge. This effect can be achieved while using membrane bioreactor technology (MBR). The experiments also showed that if dairy plants wastewater is pre-treated with coagulants and flocculants, specific speed of biocontamination oxidation decreases in 1, 2-2, 3 times at BOD full = 250 mg/l in comparison with the initial wastewater. It happens because of substrate inhibition rate of biochemical reactions. The identified dependencies show that it is advisable to exclude the stage of reagent flotation before the biological treatment of dairy products industry wastewater. It can reduce costs of using a large number of expensive reagents and simplify the technological scheme. During the experiments dairy plants wastewater was taken as a model. Later, the researchers used real wastewater and confirmed the main kinetic constants and coefficients for calculations of biological purification plants. These results are as follows: temperature constant χ, grad −1 , for aerobic heterotrophic conversion – 0,079-0,091, for nitrification – 0.096; for denitrification – 0.13. Coefficients of inhibition by active sludge φ metabolic products amounted to (l/g): for organic substances oxidation by BOD full – 0,39-0,54; for nitrification – 0.19, for denitrification – 0.22; active reaction of the environment corresponding to the highest rate of oxidation of organic substances pH opt – 6.9 at pH-constant 150. The maximum specific speed of organic substances oxidation r’ max is 82,5-101,1 mg/(g × h), the Michaelis constant K m – 15 mg/l. The maximum specific speed of nitrification r’ max is 1.49 mg/(g × h), the Michaelis constant K m is 0.12 mg/l, the constant of inhibition a is 43. The maximum specific speed of denitrification r’ max is 10.8 mg/(g × h), the Michaelis constant K m is 3.5 mg/l. The calculated values of kinetic coefficients and constants make it possible to calculate membrane bioreactors of sewage treatment plants of dairy industry to the specified degree of purification. The estimated annual economic effect for “Pestravskiy” diary plant of the Samara region equaled 4 mln. rub/year (at 2017 values).